Conventionally, as an external EGR device of this type, for example, one disclosed in PTL 1 has been known. This external EGR device is a so-called low pressure type, with an EGR passage and an EGR control valve, and is provided in an internal combustion engine together with a turbo-type supercharger. This EGR passage is connected to a downstream side of a turbine of the supercharger in an exhaust passage and to a downstream side of a throttle valve and an upstream side of a compressor of the supercharger in an intake passage, such that part of exhaust gases is recirculated to the intake passage as EGR gas via the EGR passage. Further, the amount of EGR gas recirculated to the intake passage is controlled by the EGR control valve.
Further, to the intake passage of the internal combustion engine disclosed in PTL 2, a bypass passage is connected to bypass the throttle valve. In this bypass passage, an auxiliary intake air amount control valve is provided for controlling the amount of fresh air supplied via the bypass passage to a combustion chamber of the engine. Further, in PTL 2, when the engine is in a decelerating operation state and executes a combusting operation without fuel cut, the control system controls the throttle valve to a fully-closed state and the opening degree of the auxiliary intake air amount control valve to a predetermined opening degree according to a predetermined target auxiliary air amount. The target auxiliary air amount is set to such a value as can avoid misfiring of the engine caused by shortage of the amount of fresh air due to the control of the throttle valve to the fully-closed state.